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Influence of metal alloy and the profile of coronary stents in patients with multivessel coronary disease

ABREU FILHO, Luciano Maurício de; FORTE, Antonio Artur da Cruz; SUMITA, Marcos Kiyoshi; FAVARATO, Desidério; MEIRELES, George Cesar Ximenes
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.35%
BACKGROUND: In Brazil, despite the recommendations of the Brazilian Society of Hemodynamics and Interventional Cardiology, the National Health System has not yet approved the use of drug-eluting stents. In percutaneous coronary interventions performed in the public and part of the private health care system, bare metal stents are used as the only option. Therefore, new information on bare metal stents is of great importance. The primary endpoint was to evaluate the influence of the alloy and the profile of coronary stents on late loss and restenosis rates 6 months after implantation in patients with multivessel coronary disease. METHODS: Single center, randomized and prospective study comparison of cobalt-chromium versus stainless steel stent implantation in 187 patients with multivessel coronary disease. At least one cobalt-chromium and one stainless steel stent were implanted per patient. RESULTS: Mean age of patients was 59.5 + 10.1 years with a prevalence of males (66.3%) and patients with acute coronary syndrome (56%). Baseline clinical characteristics were similar with hypertension in 146 (78%), dyslipidemia in 85 (45.5%) and diabetes in 68 (36.4%). Two hundred and twenty-nine cobalt-chromium and 284 stainless steel stents were implanted. Angiographic variables showed no statistically significant difference. Angiographic follow-up to 6 months after implantation showed similar late loss and restenosis rates. CONCLUSION: The use of two different alloys...

Comportamento de desgaste de pares Metal-Compósito de grau aeronáutico; Wear behavior of aeronautical grade metal / composite pairs

Freitas, Amilton Joaquim Cordeiro de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/06/2009 PT
Relevância na Pesquisa
46.38%
Estudou-se o comportamento de desgaste sob deslizamento em múltiplos passes de pinos fixos de liga metálica friccionados contra discos rotativos de laminados compósitos de matriz polimérica fortalecidos com fibras contínuas de carbono (C), para distintas cargas aplicadas e temperaturas de ensaio. Determinou-se a perda de volume por desgaste dos diversos pares tribológicos, e avaliaram-se os principais aspectos das superfícies e dos produtos gerados durante o processo de desgaste. Concluiu-se que o par formado pelo aço inoxidável martensítico PH 15-5 e o laminado compósito termoplástico C-PPS (poli-sulfeto de fenileno) apresentou o menor desgaste na maioria das circunstâncias avaliadas. A liga Ti6Al4V foi a pior opção dentre os pinos metálicos, independentemente do laminado compósito empregado, devido à baixa resistência ao cisalhamento e alta rugosidade superficial do metal, a qual prejudicou o ancoramento de filmes poliméricos de transferência. O ótimo desempenho do aço PH resultou de sua alta dureza e da adequada rugosidade superficial para o efetivo ancoramento do filme de transferência. O laminado compósito C-PPS se mostrou mais susceptível às variações na carga de contato, enquanto que o C-EPX (Epóxi) foi mais sensível à temperatura de ensaio. Filmes poliméricos de transferência atuaram como lubrificante do sistema tribológico...

Análise da distribuição de tensões em implantes suporte de prótese total fixa em função do número e inclinação dos implantes, tipo de liga, presença ou ausência de cantilever e forma da secção transversal da infraestrutura; Analysis of stress transfer in fixed complete prosthese supporting implants varying the number of implants, cast metal alloy, presence or absence of cantilever, angulation of distal implants and superstructure cross-sectional shape

Pinto, Humberto Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/06/2011 PT
Relevância na Pesquisa
66.45%
A fotoelasticidade é um método analítico usado para avaliar e calcular as tensões existentes em qualquer ponto da superfície de um material. É uma ferramenta para análise de tensões bidimensionais, usa luz monocromática polarizada e modelos de resina. O objetivo do presente estudo foi comparar as tensões induzidas na interface osso-implante em diferentes planejamentos de próteses fixas totais implantossuportadas protocolo de Branemark. As variáveis nos modelos foram: número de implantes, tipo de liga, presença ou ausência de cantilever, inclinação dos implantes distais e secção transversal da infraestrutura. Foram confeccionados 32 modelos fotoelásticos e foram realizadas análises qualitativa e quantitativa das tensões induzidas. Os modelos sofreram carga estática no valor de 50 N na porção central e distal da barra. Os implantes central e distal foram analisados sob as cargas central e distal individualmente. Os pilares receberam torque de 20 N.cm e os parafusos protéticos de fixação da barra receberam 10 N.cm. Antes de qualquer avaliação, foi certificado que os modelos fotoelásticos encontravam-se livres de tensões residuais. A tensão (MPa) acumulada nos implantes distais sob carga distal foi aproximadamente 7 vezes maior que nas outras situações de carga. Além disso...

A Comparison of Deep Drawing and Ironing of Metal Alloy Strip Produced conventionally and Non-conventionally via Semi Solid Material Processing

Lima Filho, Antonio de Padua; Yamasaki, Marcio Luji; Ono, Leandro Akita; Nampo, Lourenco; Padilha, Alcides; Hirt, G; Rassili, A; BuhrigPolaczek, A
Fonte: Trans Tech Publications Ltd Publicador: Trans Tech Publications Ltd
Tipo: Conferência ou Objeto de Conferência Formato: 49-54
ENG
Relevância na Pesquisa
46.21%
A semi solid thin strip continuous casting process was used to obtain 50%wt Pb/50%wtSn strip by single and twin roll processing at speed of 15 m/min. A 50%wt Pb/50%wtSn plate ingot was also cast for rolling conventionally into strips of 1.4 mm thickness and 45 mm width for comparison with those achieved non-conventionally. This hypoeutectic alloy has a solidification interval and fusion temperature of approximately 31 degrees C and 215 degrees C respectively. The casting alloy temperature was around 280 degrees C as measured by a type K immersion thermocouple prior to pouring into a tundish designed to maintain a constant melt flow on the cooling slope during semi solid material production. A nozzle with a weir ensures that the semi solid material is dragged smoothly by the lower roll, producing strip with minimum contamination of slag/oxide. The temperatures of the cooling slope and the lower roll were also monitored using K type thermocouples. The coiled semi solid strip, which has a thickness of 1.5 mm and 45 mm width, was rolled conventionally in order to obtain 1.2 mm thick strip. The coiled thixorolled strip had a thickness of 1.2 mm and achieved practically the same width as the conventional strips. Blanks of 40 mm diameter were cut from the strips in a mechanical press...

EFFECT of DIFFERENT AIRBORNE-PARTICLE ABRASION/BONDING AGENT COMBINATIONS on THE BOND STRENGTH of A RESIN CEMENT TO A BASE METAL ALLOY

Fonseca, Renata Garcia; Martins, Samira Branco; Abi-Rached, Filipe de Oliveira; dos Santos Cruz, Carlos Alberto
Fonte: Mosby-elsevier Publicador: Mosby-elsevier
Tipo: Artigo de Revista Científica Formato: 316-323
ENG
Relevância na Pesquisa
36.63%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 09/06202-9; Statement of problem. Investigation of surface treatments to improve the bond of resin cements to metals may contribute to the longevity of metal ceramic restorations.Purpose. The purpose of this study was to evaluate the efficacy of surface treatments on the shear bond strength (SBS) of a resin cement to nickel-chromium (NiCr) alloy.Material and methods. Eighty cast NiCr alloy disks (9 x 3 mm) were divided into 8 groups (n=10), which received 1 of the following surface treatments: 1) 50 mu m Al2O3 particles + silane; 2) 120 mu m Al2O3 + silane; 3) 30 mu m silica-modified Al2O3 (Cojet Sand) + silane; 4) 120 mu m Al2O3 followed by 110 mu m silica-modified Al2O3 (Rocatec) + silane; 5) 50 mu m Al2O3 + metal primer; 6) 120 mu m Al2O3 + metal primer; 7) 30 mu m silica-modified Al2O3 (Cojet Sand) + metal primer; and 8) 120 mu m Al2O3 followed by 110 mu m silica-modified Al2O3 (Rocatec) + metal primer. The silane was RelyX Ceramic Primer and the metal primer Alloy Primer. RelyX ARC resin cement was bonded to NiCr alloy surfaces. Specimens were thermally cycled before shear mode testing. Data (MPa) were analyzed by 1-way ANOVA and the Tukey test (alpha=.05). Failure mode was determined with a stereomicroscope (x20).Results. The results revealed that surface treatment was significant (P<.001). There was no significant difference between 50 mu m and 120 mu m Al2O3 particles...

Caracterização de revestimento de titânia aplicado por aspersão térmica a plasma em liga Ti-6A1-4V para aplicação em implantes; Characterization of titania coatings by thermal plasma sprayed in Ti-6A1-4V alloy for application in implants

Fernando de Almeida Gonçalves
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/02/2012 PT
Relevância na Pesquisa
36.57%
A necessidade de melhorar as características superficiais da liga Ti-4Al-6V usada em implantes ortopédicos, levou à pesquisas no sentido de estudar a modificação da superfície dos implantes através da deposição de revestimentos cerâmicos resistentes à corrosão, ao desgaste e biocompatíveis, por vários métodos: eletroquímica, física a vapor, eletroforética, por sol-gel, biomimética e por aspersão térmica a plasma, entre outras. A aspersão térmica a plasma é o processo mais utilizado comercialmente, pois é rápido e reprodutível. As biocerâmicas mais utilizadas para revestimento, com sucesso, são as de fosfato de cálcio (hidroxiapatita-HA, betafosfato tricálcico [o -TCP] e uma mistura dessas duas fases). A adesão dessas biocerâmicas ao tecido ósseo possuí bom desempenho é bastante discutida na literatura. A comunidade médica tem algumas restrições ao uso desses implantes metálicos revestidos por cerâmicas, com relação à interface metal-cerâmica, cuja adesão é considerada baixa. Neste trabalho foi estudado a adesão metal/cerâmica em implantes revestidos por aspersão térmica à plasma (ATP) com cerâmica, mais especificamente liga de titânio (Ti-6Al-4V) revestida com titânia (TiO2) sem e com tratamento térmico a vácuo...

Interfaces metal-porcelana dentária : estudos de molhabilidade em novos sitemas de ligação

Pereira, Jorge Carlos Lopes Brás Silva
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Dissertação de Mestrado
Publicado em 07/03/2007 POR
Relevância na Pesquisa
36.57%
Interfaces metal/cerâmico estão presentes em alguns sistemas de restauração dentária, tais como coroas, pontes e implantes. Os fenómenos de molhabilidade, espalhamento e adesão têm um papel importante nestes sistemas, os quais muitas vezes exibem falhas e rupturas, tendo como consequências o sofrimento e custos de substituição para o paciente. As falhas acima mencionadas devem-se sobretudo a uma fraca adesão, diferenças acentuadas no coeficiente de expansão térmica entre os materiais e a mudanças bruscas das propriedades mecânicas na região interfacial. Uma tentativa de eliminar ou reduzir esses problemas, poderá ser a introdução de um outro material para reagir e criar novas interfaces entre a liga dentária e a porcelana. A utilização de ligas de brasagem activas é uma da técnica comum para a ligação metal-cerâmico. Normalmente envolve reacções interfaciais complexas entre a liga de brasagem e o sistema metal-cerâmico, resultando num sistema multicamada. Quando correctamente elaborado (correcta selecção de materiais, perfeita molhabilidade e adesão e adequado ciclo térmico), este sistema multicamada fornece uma transição suave entre a parte metálica dúctil e a porcelana frágil...

Influence of metal alloy and the profile of coronary stents in patients with multivessel coronary disease

Abreu Filho,Luciano Maurício de; Forte,Antonio Artur da Cruz; Sumita,Marcos Kiyoshi; Favarato,Desidério; Meireles,George Cesar Ximenes
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
46.35%
BACKGROUND: In Brazil, despite the recommendations of the Brazilian Society of Hemodynamics and Interventional Cardiology, the National Health System has not yet approved the use of drug-eluting stents. In percutaneous coronary interventions performed in the public and part of the private health care system, bare metal stents are used as the only option. Therefore, new information on bare metal stents is of great importance. The primary endpoint was to evaluate the influence of the alloy and the profile of coronary stents on late loss and restenosis rates 6 months after implantation in patients with multivessel coronary disease. METHODS: Single center, randomized and prospective study comparison of cobalt-chromium versus stainless steel stent implantation in 187 patients with multivessel coronary disease. At least one cobalt-chromium and one stainless steel stent were implanted per patient. RESULTS: Mean age of patients was 59.5 + 10.1 years with a prevalence of males (66.3%) and patients with acute coronary syndrome (56%). Baseline clinical characteristics were similar with hypertension in 146 (78%), dyslipidemia in 85 (45.5%) and diabetes in 68 (36.4%). Two hundred and twenty-nine cobalt-chromium and 284 stainless steel stents were implanted. Angiographic variables showed no statistically significant difference. Angiographic follow-up to 6 months after implantation showed similar late loss and restenosis rates. CONCLUSION: The use of two different alloys...

Comparison of the Effect of Different Ceramic Alloys and Porcelain Systems upon the Color of Metal–Ceramic Restorations: An In Vitro Study

Anitha, K. V.; Dhanraj, M.; Haribabu, R.
Fonte: Springer India Publicador: Springer India
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.63%
The exact replication of natural tooth color in a metal ceramic restoration is a challenging fact as its affected by enumerable factors. Research revealing the influence of base metal alloys with different porcelain systems on the color of the restorations have shown minimal interest. The aim of the study was to evaluate the optical influence of different alloys (mainly base metal) and ceramic systems affecting the final color of metal–ceramic restorations. Four commercial ceramic alloys, two Ni–Cr, one Co–Cr and a high-noble alloy were combined with two porcelains in metal–ceramic specimens with a standardized thickness of layers. Ten disc-shaped specimens were prepared for each alloy/porcelain combination. High-noble was used as control group. Only opaque and dentin layers were applied. The specimens were analysed with Spectrophotometer, and data were obtained in the CIELAB color system. The recorded data were analysed with a one-way ANOVA and multiple range test by tukey—HSD procedure to identify the significant groups at 5 % level. The final color of the metal–ceramic specimens were significantly affected by both type of the alloy and the porcelain systems used (P < 0.0001). The Co-Cr alloy-porcelain combination produced least color difference when compared with the high-noble control group. There was significant difference (P < 0.0001) between both the brands of Ni–Cr alloy–porcelain systems. For all the alloy-porcelain combinations VMK 95 porcelain showed minimum color difference compared to the d-SIGN porcelain group. Conclusion: The final color of metal ceramic specimens was influenced both from the type of base metal alloy substructure and from the type of overlying porcelain.

Improved reversibility in lithium-oxygen battery: Understanding elementary reactions and surface charge engineering of metal alloy catalyst

Kim, Byung Gon; Kim, Hyung-Jin; Back, Seoin; Nam, Kwan Woo; Jung, Yousung; Han, Young-Kyu; Choi, Jang Wook
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 27/02/2014 EN
Relevância na Pesquisa
46.28%
Most Li-O2 batteries suffer from sluggish kinetics during oxygen evolution reactions (OERs). To overcome this drawback, we take the lesson from other catalysis researches that showed improved catalytic activities by employing metal alloy catalysts. Such research effort has led us to find Pt3Co nanoparticles as an effective OER catalyst in Li-O2 batteries. The superior catalytic activity was reflected in the substantially decreased overpotentials and improved cycling/rate performance compared to those of other catalysts. Density functional theory calculations suggested that the low OER overpotentials are associated with the reduced adsorption strength of LiO2 on the outermost Pt catalytic sites. Also, the alloy catalyst generates amorphous Li2O2 conformally coated around the catalyst and thus facilitates easier decomposition and higher reversibility. This investigation conveys an important message that understanding elementary reactions and surface charge engineering of air-catalysts are one of the most effective approaches in resolving the chronic sluggish charging kinetics in Li-O2 batteries.

Comparative study of bond characteristics between titanium/titanium alloy and ceramic; Comparative study of bond characteristics between titanium/titanium alloy and ceramic; Die vergleichende Untersuchung von Verbundeigenschaft zwischen Reintitan/Titanlegierung und Keramik

Lee, Ho-Rim
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.58%
Heutzutage ist der Gebrauch Titan-keramischer Restauration vermehrt, aber es gibt einige Probleme, die gelöst werden müssen. Um die Festigkeit von unlegiertem Titan zu verbessern, wurde die TiAl6Nb7 Legierung entwickelt, die einen höheren Wärmeausdehnungskoeffizient im Vergleich zu Reintitan hat. Aufgrund der verschiedenen Wärmeausdehnungskoeffizienten und elastischen Eigenschaften von Titan/Titan Legierung und verblendeter Keramik, beeinflusst die entstehende Spannung die metallkeramische Kompatibilität. Der Tübinger Gabel Test wurde entwickelt, um die thermische Kompatibilität zwischen Metall und verblendeter Keramik experimentell bewerten zu können. Das Ziel dieser Untersuchung sollte sein, die effektive thermische Kontraktionsdifferenz zu berechnen und die Verbundfestigkeit am System Reintitan/TiAl6Nb7 Legierung mit Keramik zu messen. Gabelförmige Prüfkörper mit zwei parallelen Ästen wurden von Reintitan Grade 2 und TiAl6Nb7 Legierung mit dem Einkammer-Vakuum-Druckgussgerät mit Lichtbogen-Schmelzeinrichtung gegossen. Nach der Oberflächebearbeitung mit SiC 1200 und Reinigen in Äthylalkohol, wurde Titankeramik auf der entgegengesetzten Seite jeden Astes gemäß Herstellerangaben verblendet. Nach dem Abkühlen wurde der Abstand der Durchbiegung der zwei Äste mit dem Mikroskop an der Front der Äste gemessen. Auf der Basis dieser Daten wurde die effektive thermische Kontraktionsdifferenz zwischen rein Titan/TiAl6Nb7 Legierung und Keramik berechnet. Der Dreipunktbiegeversuch nach Schwickerath wurde gemäß ISO 9693 durchgeführt...

Comparaison de la force d'adhésion de deux types de résines de collage appliquées sur des surfaces métalliques traitées de différentes façons : une étude in vitro

Naseri, Lyna
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
46.56%
L’objectif de cette étude était d’évaluer et de comparer la force d’adhésion de deux résines de collage: le ClearfilTM Esthetic Cement & DC Bond Kit (C) et le RelyXTM Unicem (R), sur trois adhérents différents : une surface d’émail, un alliage de métaux non précieux (Np) et un alliage de métaux semi-précieux (Sp). La surface des échantillons des alliages métalliques a subi différents traitements de surface. Sur l’émail (n=15) ainsi que sur les plaquettes d’alliages Np et Sp (n=15), des cylindres de résine étaient appliqués et polymérisés. Suite au processus de collage, les échantillons ont été incubés à 37°C pendant 24 heures, puis ont subi 500 cycles de thermocyclage. Des tests de cisaillement ont été effectués, suivi par l’analyse de la surface des échantillons au microscope à balayage électronique. Une comparaison de type T-test et des comparaisons multiples post hoc, ont été effectuées pour l’analyse statistique (p 0,05). Sur l’émail, les résultats ont démontré que la résine C présentait une force d'adhésion moyenne statistiquement supérieure (33,97±17,18 MPa) à la résine R (10,48±11,23 MPa) (p 0,05). Le type d’alliage utilisé n’influençait pas la force d’adhésion...

Correlation between metal-ceramic bond strength and coefficient of linear thermal expansion difference

LOPES, Stella Crosara; PAGNANO, Valéria Oliveira; ROLLO, João Manuel Domingos de Almeida; LEAL, Mônica Barbosa; BEZZON, Osvaldo Luiz
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.57%
The purpose of this study was to evaluate the metal-ceramic bond strength (MCBS) of 6 metal-ceramic pairs (2 Ni-Cr alloys and 1 Pd-Ag alloy with 2 dental ceramics) and correlate the MCBS values with the differences between the coefficients of linear thermal expansion (CTEs) of the metals and ceramics. Verabond (VB) Ni-Cr-Be alloy, Verabond II (VB2), Ni-Cr alloy, Pors-on 4 (P), Pd-Ag alloy, and IPS (I) and Duceram (D) ceramics were used for the MCBS test and dilatometric test. Forty-eight ceramic rings were built around metallic rods (3.0 mm in diameter and 70.0 mm in length) made from the evaluated alloys. The rods were subsequently embedded in gypsum cast in order to perform a tensile load test, which enabled calculating the CMBS. Five specimens (2.0 mm in diameter and 12.0 mm in length) of each material were made for the dilatometric test. The chromel-alumel thermocouple required for the test was welded into the metal test specimens and inserted into the ceramics. ANOVA and Tukey's test revealed significant differences (p=0.01) for the MCBS test results (MPa), with PI showing higher MCBS (67.72) than the other pairs, which did not present any significant differences. The CTE (10-6 oC-1) differences were: VBI (0.54), VBD (1.33), VB2I (-0.14)...

Correlation between metal-ceramic bond strength and coefficient of linear thermal expansion difference

Lopes,Stella Crosara; Pagnano,Valéria Oliveira; Rollo,João Manuel Domingos de Almeida; Leal,Mônica Barbosa; Bezzon,Osvaldo Luiz
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2009 EN
Relevância na Pesquisa
36.57%
The purpose of this study was to evaluate the metal-ceramic bond strength (MCBS) of 6 metal-ceramic pairs (2 Ni-Cr alloys and 1 Pd-Ag alloy with 2 dental ceramics) and correlate the MCBS values with the differences between the coefficients of linear thermal expansion (CTEs) of the metals and ceramics. Verabond (VB) Ni-Cr-Be alloy, Verabond II (VB2), Ni-Cr alloy, Pors-on 4 (P), Pd-Ag alloy, and IPS (I) and Duceram (D) ceramics were used for the MCBS test and dilatometric test. Forty-eight ceramic rings were built around metallic rods (3.0 mm in diameter and 70.0 mm in length) made from the evaluated alloys. The rods were subsequently embedded in gypsum cast in order to perform a tensile load test, which enabled calculating the CMBS. Five specimens (2.0 mm in diameter and 12.0 mm in length) of each material were made for the dilatometric test. The chromel-alumel thermocouple required for the test was welded into the metal test specimens and inserted into the ceramics. ANOVA and Tukey's test revealed significant differences (p=0.01) for the MCBS test results (MPa), with PI showing higher MCBS (67.72) than the other pairs, which did not present any significant differences. The CTE (10-6 oC-1) differences were: VBI (0.54), VBD (1.33), VB2I (-0.14)...

Numerical study of the influence of an applied electrical potential on the solidification of a binary metal alloy

Nikrityuk, P. A.; Eckert, K.; Grundmann, R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/07/2007
Relevância na Pesquisa
46.18%
In this work we study numerically the influence of a homogeneous electrical field on the fluid and heat transfer phenomena at macroscale and mesoscale during unidirectional solidification of a binary metal alloy. The numerical results showed that a pulse electric discharging applied perpendicularly to the solidification front leads to a much stronger Joule heating of the liquid phase in comparison to the solid phase. It was found that on the mesoscopic scale the electric current density is not homogeneous due to the complex shape of the dendrite and the difference between electrical conductivities of the solid and liquid phases. This inhomogeneity of the electrical current density in the mushy zone leads to the increase of the Joule heating of the dendrite in comparison to the interdendritic liquid and induces a pinch force (electromagnetic Lorentz force). The main features of the resulting convection in the interdendritic liquid are discussed.; Comment: 13 pages, Con. Cast Conf, Ulm 2005, Germany

Signatures of a quantum Griffiths phase in a d-metal alloy close to its ferromagnetic quantum critical point

Schroeder, Almut; Ubaid-Kassis, Sara; Vojta, Thomas
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.18%
We report magnetization ($M$) measurements close to the ferromagnetic quantum phase transition of the d-metal alloy Ni$_{1-x}$V$_x$ at a vanadium concentration of $x_c \approx 11.4 %$. In the diluted regime ($x>x_c$), the temperature ($T$) and magnetic field ($H$) dependencies of the magnetization are characterized by nonuniversal power laws and display $H/T$ scaling in a wide temperature and field range. The exponents vary strongly with $x$ and follow the predictions of a quantum Griffiths phase. We also discuss the deviations and limits of the quantum Griffiths phase as well as the phase boundaries due to bulk and cluster physics.; Comment: 4 pages, 5 figures, final version as published in the Strongly Correlated Electron Systems special issue of J. Phys. Condens. Matter

Efeito de um primer para metais sobre a força de união da interface metal-resina; Effect of a metal primer on the bond strength of the resin-metal interface

Freitas, Anderson Pinheiro de; Francisconi, Paulo Afonso Silveira
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/06/2004 ENG
Relevância na Pesquisa
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Para avaliar o efeito de diferentes tratamentos superficiais sobre a resistência ao cisalhamento da união entre uma liga metálica (Co-Cr-Mo - Remanium CD) e um cimento resinoso (Rely X TM) e analisar o tipo de fratura durante a separação dos espécimes, quarenta pares de discos metálicos foram fundidos, regularizados e polidos, submetidos a quatro ciclos térmicos (vácuo, 960ºC, 8 minutos) e divididos aleatoriamente em quatro grupos. Cada grupo recebeu um tipo de tratamento: Grupo PSP: Polimento com lixa d'água Nº 600; Grupo PCP: Polimento com lixa 600 e aplicação do condicionador metálico Alloy Primer (Kuraray); Grupo JSP: Jato de óxido de alumínio de 100µm, e Grupo JCP: Jato de óxido de alumínio de 100mm, e aplicação do Alloy Primer. Os grupos foram cimentados e armazenados em água destilada a 37ºC por 36 horas e submetidos ao ensaio de resistência ao cisalhamento. A média e o desvio padrão (em kgf/cm²) obtidos para cada grupo foram: PSP 4,0/0,4; PCP 88,9/33,6; JSP 163,2/27,6; JCP 144,5/54,0. Após a análise estatística os autores concluíram que: os maiores valores foram produzidos pelos grupos jateados (JSP, JCP), independentemente da aplicação do primer; o Alloy Primer aumentou a retentividade entre o cimento Rely X e a superfície polida da liga de Co-Cr-Mo...

Influence of metal alloy and the profile of coronary stents in patients with multivessel coronary disease

Abreu Filho, Luciano Maurício de; Forte, Antonio Artur da Cruz; Sumita, Marcos Kiyoshi; Favarato, Desidério; Meireles, George Cesar Ximenes
Fonte: Universidade de São Paulo. Faculdade de Medicina Publicador: Universidade de São Paulo. Faculdade de Medicina
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; ; Formato: application/pdf
Publicado em 01/01/2011 ENG
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BACKGROUND: In Brazil, despite the recommendations of the Brazilian Society of Hemodynamics and Interventional Cardiology, the National Health System has not yet approved the use of drug-eluting stents. In percutaneous coronary interventions performed in the public and part of the private health care system, bare metal stents are used as the only option. Therefore, new information on bare metal stents is of great importance. The primary endpoint was to evaluate the influence of the alloy and the profile of coronary stents on late loss and restenosis rates 6 months after implantation in patients with multivessel coronary disease. METHODS: Single center, randomized and prospective study comparison of cobalt-chromium versus stainless steel stent implantation in 187 patients with multivessel coronary disease. At least one cobalt-chromium and one stainless steel stent were implanted per patient. RESULTS: Mean age of patients was 59.5 + 10.1 years with a prevalence of males (66.3%) and patients with acute coronary syndrome (56%). Baseline clinical characteristics were similar with hypertension in 146 (78%), dyslipidemia in 85 (45.5%) and diabetes in 68 (36.4%). Two hundred and twenty-nine cobalt-chromium and 284 stainless steel stents were implanted. Angiographic variables showed no statistically significant difference. Angiographic follow-up to 6 months after implantation showed similar late loss and restenosis rates. CONCLUSION: The use of two different alloys...

Rapid, room temperature, high-density hydrogen adsorption on single-walled carbon nanotubes at atmospheric pressure assisted by a metal alloy

Heben, Michael; Dillon, Anne; Gennett, Thomas; Alleman, Jeffrey; Parilla, Philip; Jones, K.; Hornyak, G.
Fonte: Materials Research Society 2000 Fall Meeting: Symposium A: Nanotubes and Related Materials Publicador: Materials Research Society 2000 Fall Meeting: Symposium A: Nanotubes and Related Materials
Tipo: Abstract Formato: 26759 bytes; application/pdf
EN_US
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Laser-generated, carbon single-walled nanotubes (SWNTs) adsorb hydrogen in a matter of minutes at room temperature and atmospheric pressure in the presence of a Ti-6Al-4V metal alloy. The unusual hydrogen adsorption properties are activated when the SWNTs are sonicated in nitric acid with a Ti-6Al-4V probe. The process cuts the SWNTs and introduces ~15-40 wt% metal alloy into the previously pure single-walled nanotube material. Subsequent hydrogen adsorption occurs in two separate sites with a maximum adsorption capacity of ~7 wt% on a total sample weight basis. Approximately 2.5 wt% hydrogen is evolved at 300 K while the remainder desorbs between 475-850 K. The pure metal alloy adsorbs ~ 2.5 wt% H2, and evolves hydrogen with increasing temperature in a manner similar to the alloy-doped SWNTs. However, it is clear from studies presented here that the SWNT fraction is quite active in H2 uptake, adsorbing as much as 7 % on a SWNT weight basis.; Article may be found at: http://www.mrs.org/s_mrs/bin.asp?CID=2385&DID=54951&DOC=FILE.PDF; This work was supported by the Office of Science, Basic Energy Sciences, Division of Materials Science and the Office of Energy Efficiency and Renewable Energy Hydrogen Program of the Department of Energy under Grant No. DE-AC36-99GO10337...

A study of metal dusting corrosion on Fe- and Ni-based alloys

Mulaudzi,F.M.L.; Cornish,L.A.; Slabbert,G.A.; Papo,M.J.; Zhang,J.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2013 EN
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Behaviour studies of metal dusting processes and associated filamentous carbon formation were undertaken on Alloys 600, 601, and 800 using a simulated metal dusting environment of 25CO-70H2-5H2O (vol.%) at 650°C. These samples were studied visually and by optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDX) and X-ray diffraction (XRD). Visual examination and SEM surface observation showed that Alloy 800 suffered metal dusting attack at an early exposure reaction period. The coke deposit amounts increased significantly with reaction time from 168 hours to 336 hours in Alloys 600, 601, and 800. Alloy 800 showed pitting after 168 hours' exposure, and the degree of pitting increased after 336 hours. XRD showed all these alloys had a common austenitic phase, with Alloy 800 also having ferritic metal particles. Alloy 800 after 168 hours' exposure had a complex phase mixture on the surface, consisting of ferritic Fe and austenitic FeNi phases. For coke deposit, there were also Fe3O4, Fe3C and graphitic carbon. The existence of Fe, Ni, and Cr metal particles, and also graphitic carbon in coke deposits, was confirmed by EDX analyses.